An electronic-scanning antenna is an antenna with an array of radiating elements which comprises electronic devices allowing changes of states of the shape of the transmitted beam. Depending on their nature, these electronic devices (phase-shifters, attenuators), which are connected to the N radiating elements so as to form N active channels, act on the shape, the direction, the frequency or the polarization of the wave formed.
An active electronic-scanning antenna corresponds to an antenna whose devices for amplifying the transmitted or received signals are included in the antenna and distributed as close as possible to the radiating elements, forming an array of active transmit and receive channels. Conventionally, in reception the signals arising from the N radiating elements are grouped together after amplification, weighting and phase-shifting by physical devices called distributers or summators so as to form four sectors of identical general shape commonly called “antenna quarters”. These 4 quarters are thereafter combined together by a physical device incorporated into the antenna and called a “channel formatter” which forms the conventional deviometry channels used in radars or seekers in particular, these channels being the sum channel Σ, the bearing difference channel ΔB and the elevation difference channel ΔE.
A sectorized active electronic-scanning antenna is an antenna which does not group the N radiating elements together directly to form the four sectors and then the conventional deviometry channels but performs M partial groupings thereof, each containing a certain number of channels. These partial groupings go by the name of sector channels and are available at antenna output. A sectorized antenna can continue to give access to the conventional deviometry channels as a supplement to the outputs of the sector channels. The deviometry signals are processed conventionally while the signals arising from the sectors are used by the system whatever it be (radar, seeker, . . . ) to form, by computation a certain number of channels: the conventional deviometry channels for example but also any other type of combination of the signals arising from the M sectors which are intended to improve the information processing. Thus, in addition to the formulation of the conventional deviometry channels, a sectorized antenna formulates output signals of sector channels corresponding to the partial and disjoint groupings of a certain number of active channels of the antenna. The fact of having access to these various sector signals makes it possible to recompose by computation a CBF signal according to all combinations of the type:Signal_CBF=Σi=1MBiejψi·Channel_sector(i)  (1)where M is the number of sectors, Channel_sector(i) the signal arising from the sector of order i, and Biejψi a complex weight assigned to sector i. In practice M is a multiple of 4, M is for example equal to 16 or 32.
Hereinafter, equation (1) will be called the CBF equation.
Hereinafter also, the following terminology will be used:                Active channel: one of the N unitary channels of which the antenna is composed;        Conventional deviometry channel: one of the three deviometry channels conventionally formulated in a traditional electronic-scanning antenna;        Sector channel: one of the M sector channels formulated by a sectorized antenna;        Antenna Channel: generic term designating a sector channel or a conventional channel.        
The adjustment of active antennas involves a so-called calibration phase which consists in measuring on the assembled antenna the dispersions of amplitude and of phase in transmission or reception on the N various active channels of the antenna, these dispersions being due in particular to the dispersions of the components included in the active channels as well as to the assemblage dispersions. These dispersions are thereafter compensated by appropriate corrections applied to the amplitude control and phase control of each active channel by virtue of the pointing computer. In the case of a conventional antenna, this calibration is traditionally done at the antenna output on the sum channel Σ.
Within the framework of a sectorized active antenna, the conventional deviometry channels and the sector channels must be optimized simultaneously, a problem which does not actually arise for a conventional antenna.
Once calibrated with the required precision, the active antennas, be they sectorized or not, have to be tested according to a certain number of parameters (patterns, EIRP, G/T, . . . ). In the case of a sectorized antenna, the number of measurements to be made is much more significant than for a conventional antenna and increases nearly in proportion to the number of sector channels.
Thus for a sectorized antenna, the following problems arise in an acute manner:
calibration of the antenna, since several Antenna channels have to be optimized simultaneously (the conventional channels and the various sector channels) in contradistinction to a conventional antenna where the calibration is generally performed on the sum channel Σ;
testing, since a lot of data must be measured:                with a precision at least equal, or indeed increased, with respect to a conventional antenna;        in a measurement time which is of the same class as for a conventional antenna so that the schedules of the test phases do not increase in duration.        
Several documents deal with the calibration of conventional scanning antennas, this being the case in particular for the documents FR0904045, FR1103143 and FR1302928 as well as the documents by C. Renard: “Calibration et mesure faible coût d′une antenne à balayage électronique active” [Low-cost calibration and measurement of an active electronic-scanning antenna] CNES Workshop, December 1998, by E.GRORUD et al. “Design and Measurement of an active array antenna for an airborne X-band SAR/MTI Radar”, EUCAP Nice 2006 and by C. Renard: “Etalonnage des antennes aéroportées” [Calibration of airborne antennas], CCT CNES January 2009.
In the case of sectorized antennas, few or no satisfactory known solutions exist.
As regards the test measurements, the number of channels to be measured simultaneously in reception in a conventional electronic-scanning antenna is limited to the three conventional deviometry channels and the problem of the simultaneity of the measurements is conventionally solved:
either by using a multiport array analyzer capable of measuring these three conventional channels at the same time, the number of measurement ports of the analyzer not being able to be increased indefinitely and being limited in a standard manner to 8 currently;
or by multiplexing the three measurements on a conventional array analyzer comprising a reception port, the multiplexer being linked to the three outputs of the antenna to be measured and comprising switches making it possible to orient the desired channel.
The application of these schemes to an antenna that comprised for example 16 or 32 sectors to be tested in reception is not possible, either because the number of Antenna channels to be tested exceeds the simultaneous capacity of current array analyzers, or because of the trail effect in the case of multiplexed measurements. Indeed the antenna being in motion during the measurement, the Antenna channels are not all actually measured at the same location of the antenna pattern, this not being serious when the number of channels is low but which becomes crippling when the number of channels increases greatly, then causing the so-called “trail” effect.
Stopping the antenna, which is necessary for the time the measurement is being performed, leads to crippling measurement times and cannot be an acceptable solution either.